Ian has 6 more 20-cent coins than 10-cent coins. After he used 18 of his 20-cent coins, the total value of 20-cent coins is $3.40 more than the total value of 10-cent coins. How many coins did he have at first?
|
20¢ |
10¢ |
Before |
1 u + 6 |
1 u |
Change |
- 18 |
|
After |
1 u - 12 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 12 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 240 |
10 u |
$1 = 100¢
$3.40 = 340¢
Number of 20¢ coins in the end
= 1 u + 6 - 18
= 1 u - 12
Total value of 20¢ coins in the end
= 20 x (1 u - 12)
= 20 u - 240
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 18 20-cent coins, the value of 20-cent coins is 340¢ more than the value of 10-cent coins. If another 340¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 240 = 10 u + 340
20 u - 10 u = 340 + 240
10 u = 580
1 u = 580 ÷ 10 = 58
Number of coins that Ian had at first
= 1 u + 1 u + 6
= 2 u + 6
= (2 x 58) + 6
= 116 + 6
= 122
Answer(s): 122